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Community XLT / XLTE Series Owner’s Manual
5 SETUP AND OPERATION
A variety of topics are covered in these sections concerning the use of the loudspeakers. Please read them
thoroughly to ensure proper set-up, operation, and the best performance, sound quality, and reliability from your
loudspeakers.
5.1 CHOOSING A POWER AMPLIFIER
It is important to select the proper power amplifier output for the loudspeaker. To avoid the potential for damage
and less than optimum performance you need to have enough amplifier power but not too much. Note that
maximum ratings for many loudspeakers do not consider distortion. Community’s maximum power ratings are
realistically usable because they are based on keeping distortion well within acceptable limits.
5.1.1 Power Amplifier Choice
(Refer to SECTION 9.2 Using Lower Power Amplifiers)
Assuming the correct loudspeakers have been chosen for your application, the best choice of power amplifier is a
simple consideration:
A POWER AMPLIFIER WHOSE RATED POWER APPROXIMATELY MATCHES THE PROGRAM POWER RATING
OF YOUR COMMUNITY LOUDSPEAKER IS RECOMMENDED. This will provide two important benefits:
1. The PowerSense protection circuitry can operate properly to help protect the loudspeaker.
2. When average power outputs are near the RMS rating of the loudspeaker, peak power outputs of 7 dB to
10 dB will be available for the transient (or peak) content of audio signals without clipping the amplifier.
5.1.2 Power Amplifier Load Impedance
The nominal impedance of the loudspeaker (e.g. 8 Ohm or 4 Ohm) must be used as the load impedance when
determining an amplifier’s output specification from its manufacturer.
The impedances to use when using a full-range loudspeaker driven off a 51 or 55 FULL-RANGE OUTPUT, will be the
nominal impedance of the subwoofer at low frequencies and the nominal impedance of the full-range loudspeaker at
high frequencies. For example, using a 43 connected to the FULL-RANGE OUTPUT on a 55, the amplifier will
operate at 4 ohms driving the 55 and at 8 ohms driving the 43. This is because each amplifier “sees” only one
loudspeaker in each frequency range. Thus, an amplifier rated for 600W at 4 ohms and 400W at 8 ohms will deliver
up to 600W to the 55 but only up to 400W to the 43. (See to SECTION 5.2.1 for using the FULL-RANGE OUTPUT on
the 51 and 55 subwoofers.)
This is similar to what happens with a full-range loudspeaker such as the 43. Although the individual LF and HF
drivers are 8 Ohms, the impedance of the overall system is 8 Ohms because the amplifier “sees” only one driver in
each frequency range.
5.1.3 Recommended Amplifier Power for Specific Models
TABLES 3, 4, and 5 list the recommended amplifier power for all of the XLT and XLTE models. The power figures
listed indicate amplifier RMS ratings and assume this a 20 Hz – 20 kHz power rating per amplifier channel.
Specifying an exact power output is simply overly precise for the purposes of powering a loudspeaker. In addition, it
might be difficult to find an amplifier that exactly matches a precise number. Therefore, a REC. POWER AMP RANGE
(Recommended Power Amplifier Range) is listed. Choose an amplifier with a power output per channel that is within
this range at the listed POWER AMP LOAD IMPEDANCE. Example: an amplifier for a model 46 (either an XLT46 or
XLT46E) should be rated for anywhere between 400W RMS and 600W RMS per channel at 4 ohms.